The present invention is related to a reserve tank for engine coolant formed by blow molding and to a straddle-type all terrain vehicle equipped with the reserve tank.
Straddle-type all terrain vehicles (generally called xe2x80x9cATVsxe2x80x9d) are three-wheeled or four-wheeled motor cycles and are utilized in various fields such as leisure, sport competitions, and border patrols since the vehicles are capable of stably traveling over irregular grounds such as dunes, uncultivated lands and swamps with large payload.
This type of the vehicle is often equipped with a water-cooled type engine, and thus the engine is generally provided with a radiator for engine coolant as well as a reserve tank for the engine coolant.
The reserve tank is formed by blow molding a white-opaque material (e.g. polypropylene (P.P.)) and the blow molding is generally performed as follows:
(1) First, as shown in FIG. 1A, a heated length of thermoplastic tube (generally called a xe2x80x9cparisonxe2x80x9d) P of polypropylene is placed on an air nozzle between the halves of open mold M1 and M2. (2) Second, as shown in FIG. 1B, the mold halves M1 and M2 close and pinch shut the lower open end of the parison P. (3) Third, as shown in FIG. 1C, air is blown in to expand the parison P to cavities of the mold halves M1 and M2, which are usually cooled to set the parison material. (4) Last, as shown in FIG. 1D, the mold halves M1 and M2 are re-opened, and the parison (i.e., finished product) P is ejected.
The above-mentioned reserve tank may be arranged on the all terrain vehicle behind the crank case so as to be externally exposed. In this case, the reserve tank is colored to a color corresponding to the body color of the vehicle.
Coloring the reserve tank is typically done by painting, however, painting requires extensive equipment, and painting materials have a bad affinity with the polypropylene that forms the reserve tank, and easily separate therefrom. In particular, since the reserve tank of the above-mentioned arrangement is exposed to the outside of the vehicle""s body and is arranged behind the crank case, it has the problem of easily receiving scratches (these also include cracks and frays in this specification) from a rider""s boots, the stone shuttlecock, etc.
The present invention has been made with the aim of solving the above condition, and it is an object of the present invention to provide a reserve tank for engine coolant formed by a blow molding method in which an external surface of the finished product can be colored simultaneously with a blow molding process and thus make painting unnecessary, and also to provide a straddle-type all terrain vehicle equipped with the reserve tank.
In order to solve the above-mentioned condition, a reserve tank for engine coolant according to the present invention is formed by a blow molding method that comprises the steps of: forming a parison between halves of an open mold; blowing air into the parison to expand while pinching the parison between the mold halves; and forming a hollow product by cooling to harden the expanded parison pressed in cavities of the mold halves, wherein before pinching the parison between the mold halves, a thermoplastic film with a color which is different from the parison is so placed that the thermoplastic film covers at least one of the cavities, and wherein when blowing the parison, the thermoplastic film placed over the cavity is pressed along with the parison and stuck thereto.
The principle of the blow molding method of the reserve tank for engine coolant according to the present invention is explained below referring to FIGS. 2A-2D. (1) First, as shown in FIG. 2A, a heated length of thermoplastic tube (parison) P of polypropylene is placed on an air nozzle between halves of open mold M1 and M2. In this case, the thermoplastic film F, which has a desired color, is arranged so that the thermoplastic film F covers, for example, a cavity of one mold M1. (2) Second, as shown in FIG. 2B, the mold halves M1 and M2 close and pinch shut the lower open end of the parison P as well as the lower end of the thermoplastic film F. (3) Third, as shown in FIG. 2C, air is blown in to expand the parison P to the cavities of the mold halves M1 and M2, which are cooled to set the parison material. Under this condition, the thermoplastic film F is pushed between the parison P and the mold half M1 in the state where the thermoplastic film F is heat deformed and stuck on along the surface of the heated parison P. (4) The mold halves M1 and M2 are cooled in this state, and the parison P inside thereof and the thermoplastic film F are hardened in the form of the cavities. Lastly, as shown in FIG. 2D, the mold halves M1 and M2 are re-opened, and the finished reserve tank which is covered with the thermoplastic film F is ejected.
Therefore, according to the present invention, at least one of the cavities of the blow molding mold is covered with the thermoplastic film having a color different from the parison, and then in this state ordinary blow molding is performed. The blown parison is forced between the cavities while carrying out heat deformation of the thermoplastic film, and an adhesion covering of the thermoplastic film having a color different from the parison is formed on the surface of the parison with cooling.
It becomes possible for a thermoplastic film to cover the main body of the reserve tank with such composition in the same process, without making virtually any improvements to an existing blow molding machine. By using an opaque material (including a colored material) for this thermoplastic film, it replaces paint, and coloring to the external surface of the reserve tank is attained. Moreover, it is possible by adopting a suitable thermoplastic film material to protect the reserve tank surface from scratches from the outside. Using the thermoplastic film as a surface treatment is also possible. In addition, in FIGS. 2A-2D, although the thermoplastic film F is arranged only on one cavity of the mold half M1, the thermoplastic film F may cover both cavities of the mold halves M1 and M2, or may cover one of the cavities.
Moreover, in accordance with the above-mentioned blow molding method, it is also possible as a thermoplastic film to use a similar material to the parison. Thus, by constituting as above, the affinity between the thermoplastic film and the parison can be improved and strong covering which cannot be easily influenced of the scratches from the outside can be obtained.
Moreover, in accordance with the above-mentioned blow molding method, by using a transparent material for the parison and by using an opaque material (or a colored material) for the thermoplastic film, a check window (for example, in order to check quantity of contents from the outside) can be formed on the reserve tank by removing a portion of the colored thermoplastic film which is adhesively hardened on the reserve tank so as to cover thereof. Thus, it is possible to easily obtain a suitable reserve tank for engine coolant for a straddle-type all terrain vehicle which does not easily receive scratches even if it is exposed to the outside of the vehicle""s body.
In addition, as shown in FIG. 3, the thermoplastic film F can be aligned over the cavity by forming holes G at a position where the thermoplastic film F is not in contact with the cavity and by inserting bosses B formed at a position on the mold half (in this example, xe2x80x9cM1xe2x80x9d) corresponding to the holes G. Thus, it becomes possible to position the thermoplastic film F over the cavity of the mold half M1 easily.
Moreover, in accordance with the reserve tank for coolant formed by the above-mentioned blow molding method, as mentioned above, the reserve tank has a wide variety of applications because it is more resistant to scratches from the outside than common molded products which are colored with typical painting processes, it does not require any painting or surface treatment, it can be covered only one side with the thermoplastic film, and it is possible to freely expose the casting material (i.e., material of the parison) under the thermoplastic film by removing.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.